Is the Claude Agent SDK open source?

Only the Python package. claude-agent-sdk-python ships under the MIT license, copyright Anthropic PBC, so its source is public, modifiable, and redistributable. The TypeScript package, claude-agent-sdk-typescript, isn’t: its LICENSE.md says “All rights reserved,” with use governed by Anthropic’s Commercial Terms of Service, the same terms Anthropic’s own SDK overview says govern the Agent SDK generally, “except to the extent a specific component or dependency is covered by a different license as indicated in that component’s LICENSE file.” The Python package is that exception, not the rule. Either way, what the SDK wraps, the tool-calling loop that runs against the Claude Code binary, is unaffected by which license the wrapper carries; open or not, it still calls the Claude API and bills like any other Claude usage.